For various purposes, most specifically for metallurgical additive purposes, prior art workers have made combinations of highly reactive metals with less reactive metals. For example, Hardy in U.S. Pat. No. 1,922,037 discloses combining calcium with iron, Schneider in U.S. Pat. Nos. 2,492,114 and 3,501,291 discloses combining nickel and lithium and Bach et al. in U.S. Pat. No. 3,563,730 disclose pre-combining lithium or other alkali metal with various other metals in the presence of an inert liquid.
Lithium-aluminum combinations presumably made by the Bach et al. method are commercially available and have been used as sources of lithium for the manufacture of lithium-containing aluminum alloys having dispersed hardening particulates by the mechanical alloy method. Mechanical alloying which involves the milling of powders until certain criteria of uniformity and saturation hardness are reached, is a technique which can be used to make dispersion hardened alloys. When these very costly, commercially available precombined lithium-aluminum compositions are used to make lithium-containing mechanically alloyed aluminum alloys, it is difficult to maintain an alloy carbon content at a low level. Analysis of these commercially available pre-combined lithium-aluminum composition indicates a high carbon content of up to about 1% presumably as a result of paraffinic materials used as the "inert" liquid in manufacture. At present, the cost of these materials is many times the cost of the lithium contained therein. Furthermore, experience with this material indicates that the lithium content varies excessively from batch to batch.
Another source of commercially available relatively expensive lithium-aluminum master alloy is reported to make the master alloy by a complete melting of the ingredients. While this melted material appears to exhibit consistency in composition from batch to batch, its physical form is that resulting from crushing and grinding cast billet. This process is thus effectively limited to the production of relatively brittle master alloy which requires expensive crushing and grinding to obtain powder of a size useable in mechanical alloying equipment.
Since it is desirable to be able to provide mechanically alloyed lithium-containing aluminum alloy powders of low carbon content, and of any selected composition, a different means of making the pre-combination of lithium and aluminum is needed. One might say that the combination could be made simultaneously with mechanical alloying however use of free metallic lithium in a mechanical alloying apparatus (eg. an attritor) is undesirable in that it tends to gum up the attriting elements and other metal powder.